Table 2.
Relative Risks for the Joint Exposure of Purpose in Life and Income (N=13,159)a
| Sense of purpose in lifeb | Additive and multiplicative effect modification | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low | Medium–low | Medium–high | High | Low | Medium–low | Medium–high | High | ||||||||
| Household income quartile sc | n, died/alive | RR (95% CI) | n, died/alive | RR (95% CI) | n, died/alive | RR (95% CI) | n, died/alive | RR (95% CI) | Additived | Multiplicativee | Additive | Multiplicative | Additive | Multiplicative | |
| 1st quartile | 565/692 | 1.0 | 273/493 | 0.91 (0.79, 1.06); p=0.22 | 220/460 | 0.91 (0.78, 1.06); p=0.23 | 122/396 | 0.76 (0.62, 0.92); p=0.01 | ref | ref | ref | ref | ref | ref | ref |
| 2nd quartile | 353/591 | 0.93 (0.81, 1.07); p=0.33 | 252/627 | 0.87 (0.74, 1.02); p=0.09 | 205/609 | 0.81 (0.69, 0.97); p<0.01 | 140/526 | 0.78 (0.64, 0.95); p=0.01 | ref | 0.03 (−0.17, 0.22); p=0.80 | 1.02 (0.82, 1.27); p=0.83 | −0.03 (−0.23, 0.18); p=0.81 | 0.96 (0.76, 1.22); p=0.76 | 0.10 (−0.13, 0.32); p=0.40 | 1.11 (0.84, 1.47); p=0.46 |
| 3rd quartile | 234/519 | 0.98 (0.83, 1.16); p=0.83 | 176/637 | 0.78 (0.65, 0.93); p=0.01 | 187/770 | 0.76 (0.64, 0.92); p<0.01 | 105/684 | 0.58 (0.47, 0.73); p<0.01 | ref | −0.12 (−0.34, 0.11); p=0.30 | 0.87 (0.68, 1.11); p=0.25 | −0.13 (−0.35, 0.10); p=0.28 | 0.86 (0.67, 1.10); p=0.23 | −0.15 (−0.39, 0.08); p=0.21 | 0.79 (0.58, 1.07); p=0.12 |
| 4th quartile | 107/384 | 0.88 (0.70, 1.10); p=0.27 | 100/609 | 0.68 (0.54, 0.86); p=0.01 | 112/902 | 0.58 (0.46, 0.72); p<0.01 | 102/1007 | 0.55 (0.43, 0.69); p<0.01 | ref | −0.11 (−0.37, 0.15); p=0.41 | 0.85 (0.63, 1.16); p=0.31 | −0.21 (−0.47, 0.04); p=0.10 | 0.72 (0.53, 0.98); p=0.04 | −0.09 (−0.35, 0.17); p=0.50 | 0.82 (0.59, 1.15); p=0.25 |
Notes: Boldface indicates statistical significance (p<0.05).
RRs ratios were adjusted for age, gender, race/ethnicity, marital status, education, wealth, health insurance, heart disease, stroke, cancer, diabetes, hypertension, lung disease, arthritis, and depression using Poisson regression.
Purpose in life was assessed using the purpose in life subscale of the Ryff Psychological Well-being Scales. Purpose in Life Quartiles: Low: 1.00–3.86; Medium–low: 3.87–4.57; Medium–high: 4.58–5.29; High: 5.30–6.00
Household income quartiles: 1st Quartile: ≤$20,024; 2nd Quartile: $20,025–$38,321; 3rd Quartile: $38,322–$71,895; 4th Quartile: ≥$71,896
Effect modification on additive scale: relative excess risk due to interaction (RERI; SEs were calculated by using delta method).
Effect modification on multiplicative scale: ratio of risk ratio (RRR).
RR, risk ratio.